chakster
I don't like mirrors when it comes to protractors, i remember Van Den Hul protractor with mirror and it was a nighmare, because all the printed lines are reflected in the mirror and it was impossible to detect where is the actual printed line and where is the reflection of the line.It sounds like you weren't using the tool properly. The purpose of having both the actual etched line and a reflection of the line is to sight it so that those two images align perfectly. That's how you can ensure that parallax error isn't influencing the alignment.